The present invention relates to an optical cross-connect apparatus. More particularly, the invention relates to an optical cross-connect apparatus being connected to plural directions and capable of achieving an alarm indication function.
The rapid increase in the data traffic represented by the Internet has brought about large capacity transmission. Such large capacity transmission is realized in a way that the transmission signal is converted from an electrical signal to an optical signal based on time division multiplexing technology and wavelength division multiplexing technology. Currently, transmission equipment supporting 10 Gbits/s, 40 Gbits/s, and 100 Gbits/s per channel has been put into practice. Also, practical point-to-point wavelength multiplexing transmission systems can support long distance transmission over several hundreds of kilometers or more, in a way that a time divided signal of several to several tens of channels is wavelength multiplexed onto a single optical fiber, using an optical amplifier or a regenerative repeater, and the like.
In order to support a further increase in the demand for transmission capacity and to meet the requirements for further economization and diversified services, various network topologies have been introduced, such as a ring optical network in which communication nodes are connected in a closed loop (FIG. 1A), a multi-ring optical network in which plural ring optical networks are connected to each other at a connection point thereof (FIG. 1B), and a mesh optical network in which communication nodes are connected in a mesh shape in order to increase the flexibility in the route selection (FIG. 1C).
The optical transmission equipment used in the ring optical network is called an optical add/drop multiplexer (OADM). The equipment of A, B, C, and D stations in FIG. 1A, or the equipment of A, B, C, E, F, and G stations in FIG. 1B, corresponds to OADM. Further, the node located at the connection point of the multi-ring optical network and node device used in the mesh optical network are called an optical cross-connect (OXC).
Here, FIGS. 1A, 1B, and 1C are described. In FIG. 1A, a ring optical network 210 includes OADM 102 provided in each of A to D stations, and an optical fiber transmission line 101 for connecting each OADM 102 in a ring.
In FIG. 1B, a multi-ring optical network 220 includes OADMs 102 for each of A to C stations, an OXC 103 for D station, OADMs 102 for each of E to G stations, and an optical fiber transmission line 101 for connecting each OADM 102 and the OXC 103 in a ring. The OXC 103 (D station) is a common node to the first ring and the second ring.
In FIG. 1C, a mesh optical network 230 includes OXCs 103 for each of A to D stations and an optical fiber transmission line 101 for connecting each OXC 103 in a mesh form.
Such optical networks can be expected to achieve simplification of the operation of remotely managing node devices by a network supervisory system in a unified manner, facilitation of the end-to-end path management from the start to the end of the circuit by cooperation between the supervisory units of the respective node devices, as well as high speed path setting. Further, the whole network can be realized economically with a configuration that allows optical signals to pass through each node without electrical/optical conversion, based on a sophisticated optical transmission technology.
The OADM 102 and the OXC 103 use an optical switch for ADD/DROP or THROUGH selection of optical signals, and for route switching. A micro-electro-mechanical systems (MEMS) switch, which is currently known as a technology for realizing an optical switch, controls a very small mirror produced by a semiconductor technology using electrostatic power. There is also known a wavelength selective switch (WSS). The WSS has not only a simple switching function but also a wavelength division multiplexing function. In recent years, the WSS has become widely used in networks requiring connection of plural transmission lines as shown in FIGS. 1B and 1C.
Here, the operation of WSS will be briefly described with reference to FIGS. 2A and 2B. In FIG. 2A, Port_C of a 1×N WSS 104 is an input port of the WSS, and Port_1, Port_2, and Port_N are output ports of the WSS. Thus, the 1×N WSS 104 is a device including one input port and N output ports, in which a predetermined control signal is input to the input port and an arbitrary wavelength is output to any one of the ports of Port_1 to Port_N. In the example of FIG. 2A, m wavelength multiplexed signals λ1, λ2, λ3, . . . λm are input from Port_C. Then, Port_1 outputs λ1 and λ5, Port_2 outputs λ2, λ7, and λm, and Port_N outputs λ4, λ6, and λ8 to λm−1. It is to be noted that a particular wavelength, such as λ3 in FIG. 2A, can be blocked by the WSS.
In FIG. 2B, an N×1 WSS 105 with N ports input and one port output can also be realized by replacing the operation of the output port and the input port. In the N×1 WSS 105,λ1 and λ5 are input from Port—1, λ2, λ7, and λm are input from Port_2, and λ4, λ6, and λ8 to λm−1 are input from Port_N. Then, a wavelength multiplexed signal having (m−1) wavelengths, λ1 and λ2 and λ4 to λm, is output from Port_C.
The configuration of the optical add/drop multiplexer using WSS, as well as the configuration of the optical cross-connect apparatus using WSS are disclosed in JP-A No. 140598/2006, JP-A No. 262365/2006, and the like.